In e.g. automatic medical analysis instruments where a pipette arm moves a pipette at great speed between a large number of test tubes, requirements have been set up stating that the pipette must not to cause personal injuries upon an unintentional contact with the pipette during operation.
One way of accomplishing this is to completely protect the area within which the pipette moves from contact by enclosing it in a protective housing.
Since there is a need of inserting or removing test tubes during operation of the pipette, the solution with a protective housing is not satisfactory.